1.Login to your blogger dashboard--> layout- -> Edit HTML

2.Scroll down to where you see </head> tag .

3.Copy below code and paste it just before the </head> tag.

<script src='http://ajax.googleapis.com/ajax/libs/jquery/1.3.2/jquery.min.js' type='text/javascript'/>

<script type='text/javascript'>

//<![CDATA[

/*
Author: mg12
Update: 2008/05/05
Author URI: http://www.neoease.com/
*/
(function() {

function $(id) {
return document.getElementById(id);
}

function setStyleDisplay(id, status) {
$(id).style.display = status;
}

function goTop(a, t) {
a = a || 0.1;
t = t || 16;

var x1 = 0;
var y1 = 0;
var x2 = 0;
var y2 = 0;
var x3 = 0;
var y3 = 0;

if (document.documentElement) {
 x1 = document.documentElement.scrollLeft || 0;
 y1 = document.documentElement.scrollTop || 0;
}
if (document.body) {
 x2 = document.body.scrollLeft || 0;
 y2 = document.body.scrollTop || 0;
}
var x3 = window.scrollX || 0;
var y3 = window.scrollY || 0;

var x = Math.max(x1, Math.max(x2, x3));
var y = Math.max(y1, Math.max(y2, y3));

var speed = 1 + a;
window.scrollTo(Math.floor(x / speed), Math.floor(y / speed));
if(x > 0 || y > 0) {
 var f = "MGJS.goTop(" + a + ", " + t + ")";
 window.setTimeout(f, t);
}
}

function switchTab(showPanels, hidePanels, activeTab, activeClass, fadeTab, fadeClass) {
$(activeTab).className = activeClass;
$(fadeTab).className = fadeClass;

var panel, panelList;
panelList = showPanels.split(',');
for (var i = 0; i < panelList.length; i++) {
 var panel = panelList[i];
 if ($(panel)) {
  setStyleDisplay(panel, 'block');
 }
}
panelList = hidePanels.split(',');
for (var i = 0; i < panelList.length; i++) {
 panel = panelList[i];
 if ($(panel)) {
  setStyleDisplay(panel, 'none');
 }
}
}

function loadCommentShortcut() {
$('comment').onkeydown = function (moz_ev) {
 var ev = null;
 if (window.event){
  ev = window.event;
 } else {
  ev = moz_ev;
 }
 if (ev != null && ev.ctrlKey && ev.keyCode == 13) {
  $('submit').click();
 }
}
$('submit').value += ' (Ctrl+Enter)';
}

function getElementsByClassName(className, tag, parent) {
parent = parent || document;

var allTags = (tag == '*' && parent.all) ? parent.all : parent.getElementsByTagName(tag);
var matchingElements = new Array();

className = className.replace(/\-/g, '\\-');
var regex = new RegExp('(^|\\s)' + className + '(\\s|$)');

var element;
for (var i = 0; i < allTags.length; i++) {
 element = allTags[i];
 if (regex.test(element.className)) {
  matchingElements.push(element);
 }
}

return matchingElements;
}

window['MGJS'] = {};
window['MGJS']['$'] = $;
window['MGJS']['setStyleDisplay'] = setStyleDisplay;
window['MGJS']['goTop'] = goTop;
window['MGJS']['switchTab'] = switchTab;
window['MGJS']['loadCommentShortcut'] = loadCommentShortcut;
window['MGJS']['getElementsByClassName'] = getElementsByClassName;

})();


//]]>

</script>

4.Now scroll down where you see </body> tag.

5.Copy below code and paste it just before the </body> tag.

<a href='#' onclick='MGJS.goTop();return false;'><b>Go To Top</b></a>

6.Click on save template and you are done.

Demo